Starting Model Of Break Debris Flow And Its Amplification Effect Research

Wenchuan earthquake triggered a large number of mountain collapse and landslides, which provided a rich source of loose material to make debris flow happen afterthe earthquake. The landslide, collapse were formed in the channel they were deposited in the channel when the earthquake. They make the channel formed a partially or completely blocked. The most of loose material that accumulation in the channel was taken away with the surface in a short time. A small part of the accumulation of body form a weir body in a gully. In the rainy season comes, the flood washed dam body, when dam body damming, the gully occured break debris flow, it would be a catastrophic consequences. It is short time form a scale disaster, ability of damage strongly. Before the earthquake, the Break debris flows mostly occur in Tibet, in western China, and mainly belong to the glacial lake outburst debris flow, when they occured they need accumulated for a long time, frequency of outbreak are low; and after that, the ground experienced strong earthquake, several break debris flows occure in the area. The break debris flow of earthquake region different from glacial lake outburst debris flow, the earthquake region, the break debris flow accompany a long time rain, it occure time concentrate in the rainy season,and high frequency.A break debris flow is very complex, it accompanied with erosion, motion, deposit, blocking, damming. After earthquake, there happened many break debris flows in the Wenchuan,for example the Hongchun gully debris flow on August 13, 2010, the Qipan gully debris flow on July 11, 2013. To further our understanding about the type of debris flow, to provide more effective for the risk assessment of debris flow, to provide suggestions for forecasting and early warning and Engineering Management at the same time. This paper mainly has carried on the following analysis and discussion to break the debris flow about cause condition, outburst process, erosion process and motion accumulation process.The formation reasons of landslide dam have uniqueness in earthquake region. The fundamental reason of landslide dam is formed from the strong surface activity,secondly, the steep valley terrain, ravines crossbar, high mountains and narrow channel,the results make landslide dam formation with landslide, collapse and debris flow,it make solid material of landslide dam that is loose structure, high void ratio, low overall strength. This feature makes the landslide dam in the failure forms are different from other types. Natural dammed lake mainly outburst includes: instantaneous slip failure, progressive failure, erosion by overtopping. The failure way of dam’s main erosion by overtopping with break debris flow in earthquake region. This is decided by damming object itself structure features and properties, landslide dam is poor stability itself, it smaller possibility occurrence overall damage, happen localized devastation easily.We selected debris flow of larger disaster events in 2013 "7.10" that they were compared and analyzed. It analysis of the basic characteristics of debris flow about break and outburst of rainstorm debris flow, we discussed about drainage area, channel length, longitudinal slope, rate of flow, unit weight. Break debris flow commonly more serious than normal debris flow that they erosion ability of channel,the disaster is bigger, the destructive power is stronger, and the influence is more widely. The landslide dam play an important role in the formation of debris flow that is bigger and aggravate about erosion, movement.It analysis of landslide that may occur failure mode, it is very impotent for break debris flow that calculation of break discharge hydrograph. The flow process line affect the outburst of debris flow on the start time, the ability of erosion, the time of reach downstream moment, the disaster of size, it is very important for the analysis of process about debris flow,it has a value about early warning and forecasting and engineering treatment of debris flow. The peak flow of break debris flow will be earlier than normal arrival, and the burst peak flow than normal peak flow. It was calculated by the model in this paper, combined with the dam capacity, geometric shape, rock and soil characteristics, set into the flow curve, quantitative calculation of dam break flow process line, the whole process is more intuitive analysis of dam breach.For the break debris flow, the article provides a new analysis idea, using the numerical model combined with the method of theoretical analysis, we discussed the erosion process of debris flow. Break debris flow is stronger than erosion type debris flow in ability of erosion and range, when dam break flow amplification, it had remarkable effect on flow velocity, flow depth, while the erosion ability and handling the distance of the fluid in the channel, about the fluid velocity, flow depth, density and other factors. Finally determine the debris flow erosion area, we choose the debris flow erosion area of weak,and then simulation of debris flow movement and deposi-tion process. Thus we get the results of debris flow simulation is more close to the real value.We select the "7.10" in 2013 that the outbreak of Qipan gully debris flow analysis in earthquake region, first of all, to introduce and analyze the blockage point; large scale disasters blockage point in channel were calculated; the landslide dam of discharge hydrograph burst were calculated; the process of break was analyzed; we use numerical simulation software with the flow process line that analyze erosion in gully; finally, to determine the downstream Laying Rock landslide dam as debris flow movement and accumulation simulation area, The obtained the deposition range and range is closer to the actual, it provides a practical method for the analysis with such debris flow.